Scrapers or doctor blades are extensively used in the paper industry for different purposes but in most of the cases their function is to clean or scrape off material or residues from the surface of a rotating roll. A specific application of blades is constituted by their use as creping blades for the manufacture of tissue. Such blades have for a purpose to detach a paper web from a rigid dryer cylinder, usually a cast iron cylinder, by scraping the surface of the cylinder. At the same time the top or edge surface of the blade exerts a compressive action on the paper thereby creating the typical crepe structure of a tissue product.
Since creping blades are subjected to extensive wear different techniques to increase their life time are being used, such as adding wear resistant material onto the section of the blade engaging the cylinder. As an example of such reinforcement of the top or edge surface of the blade ceramic hardfacings are currently used as a practical solution to reduce the blade wear. Such ceramic coatings are usually applied to blades made of hardened and tempered carbon steel and can be applied by thermal spraying, such as plasma spraying or plating.
Examples of techniques for the provision of such wear resistant coatings onto doctor blade or scrapers are found in UK patents 978,988, 1 289 609, and 2 130 924. All this prior art is directed to the provision of a wear-resistant coating on the part of the blade engaging the surface of a rotating cylinder.